In the drilling of wells, such as oil and gas wells, it is desirable to rack the stands of drill pipe and drill collars in racking means in the derrick or beneath the floor of the derrick. Such racking apparatus necessitates the movement of successive pipe stands between racked positions and a position at the center of the derrick, and the pipe must be transferred between such positions by suitable supporting means engageable beneath the usual shoulder provided by the tool joint or coupling end of the pipe.
To conserve space in the rack, the pipe is racked in close, side by side relation in sequence, by pipe lifting and positioning means such as that disclosed in U.S. Pat. No. 3,561,811, granted Feb. 9, 1971, or in the companion application for U.S. Pat. Ser. No. 526,207, filed Nov. 22, 1974. In either case, the pipe is supported in a head which engages beneath the upset or shoulder of the tool joint to support the pipe and move it during the racking and unracking operations. A claw or retaining arm is operable to confine the pipe within the head and is pivotable to an open position to one side of the head to release the pipe. However, as the head is shifted laterally in the derrick to move pipe to and from racked positions, the claw or retaining arm precludes close racking of the pipe on one side, that is the side on which the claw or arm swings to the open position, because the claw or arm limits the proximity of the head to an adjacent pipe.
Accordingly, it has been the practice in the use of the pipe racking apparatus of the type disclosed in the above identified Pat. No. 3,561,811, either to rack pipe in widely spaced relation or to change lifting heads, depending on the direction in which the pipe is being racked, one head having a claw opening to one side and the other head having a claw opening to the other side.